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Sylvan.Data 0.2.17

Sylvan.Data

A .NET library for working with data. Provides implementations of, and extensions for, DbDataReader. All of the data operations are designed to support streaming, so large data sets don't need to fit in memory.

DataBinder

Contains a general purpose data binder that can bind DbDataReader records to object instances. The following example binds CSV data using Sylvan.Data.Csv library to strongly-typed C# Record instances.

using Sylvan.Data;
using Sylvan.Data.Csv;
using System.Linq;

using var dr = CsvDataReader.Create("data.csv");
IEnumerable<Record> records = dr.GetRecords<Record>();
Record[] allRecords = records.ToArray();

class Record {
	public int Id { get; set; }
	public string Name { get; set; }
	public DateTime Date { get; set; }
	public decimal Amount { get; set; }
}

Object data reader

The IEnumerable<T>.AsDataReader extension method provides the inverse of the databinder, exposing object instances as a DbDataReader.

This example demonstrates using the Sylvan.Data.Csv library to write object data.

IEnumerable<Record> records = GetRecords();
DbDataReader reader = records.AsDataReader();
CsvDataWriter csvWriter = CsvDataWriter.Create("records.csv");
csvWriter.Write(reader);

Extension methods

The library includes various LINQ-like extension methods for DbDataReader.

Select

Creates a DbDataReader that exposes a subset of the columns.

Where

Creates a DbDataReader that filters rows.

Skip/Take

Creates a DbDataReader that skips rows, or limits the rows read.

WithColumns

Creates a DbDataReader with additional columns attached.

This example shows how to use some of these methods in a CSV data loading operation.

using Sylvan.Data;

string csvFile = "data.csv";
var importDate = DateTime.UtcNow;
var csv = CsvDataReader.Create(csvFile);

DbDataReader dr =
	csv
	// select some of the columns from the csv file
	.Select("Id", "Name", "Date", "Value")
	// filter to just records from the last week
	.Where(d => d.GetDateTime(2) >= importDate.AddDays(-7))
	// add columns with information about the data source
	.WithColumns(
		new CustomDataColumn<string>("SourceFile", r => csvFile),
		new CustomDataColumn<DateTime>("ImportDate", r => importDate),
		new CustomDataColumn<int>("RowNum", r => csv.RowNumber)
	)
	// limit to 10k records
	.Take(10000);

LoadData(dr);

Schema

The Schema type provides methods to building and de/serializing data schema information. This can be used to attach schema information to weakly typed data files, like CSV and Excel data, using the Sylvan.Data.Csv and Sylvan.Data.Excel package.